The present invention relates to mixed powered and gravity feed overhead conveyers, which have a gravity rail section for accumulation, re-timing, workstation waiting, buffers and the like, and a suspended trolley step feeder on the gravity rail conveyer section.
As a specific powered overhead conveyor system and for specific trolleys that have a gravity rail engaging top wheel that are conventionally used in combination with a step feeder, reference is made to the following patents, whose disclosure is incorporated herein in their entirety by reference: U.S. Pat. No. 5,806,655 issued Sep. 15, 1998 to Tabler; U.S. Pat. No. 5,785,168 issued Jul. 28, 1998 to Beall Jr.: U.S. Pat. No. 4,203,511 issued May 20, 1980 to Uhing; U.S. Pat. No. 3,164,104 issued Jan. 5, 1965 to Hunt; and U.S. Pat. No. 3,850,280 issued Nov. 36, 1974 to Ohrnell.
Gravity rail conveyors are well known and generally much lighter in construction. Usually, a trolley is supported by a top wheel riding on a rail and suspending the load from the trolley, by a carriage. The trolleys, being light even when loaded may be manually pushed along the rail.
Being powered, conveyer systems of the above type can handle loads that commonly range to over one hundred pounds each, and the step feeder needs to have a substantial stop to hold upstream accumulated trolleys in line on a gravity section while the lead trolley is released. Transfer devices are known to automatically move a loaded trolley between the powered and gravity sections, and such transfer may be accomplished manually also.